D’YOUVILLE COLLEGE
PMD 604 - ANATOMY, PHYSIOLOGY, PATHOLOGY II
Lecture 10: Male & Female Reproductive Systems
G & H chapters 80 & 81
1.
Anatomy of Male Reproductive Tract (fig. 80 - 1 & ppt. 1):
• testes: primary sex organs suspended via spermatic cord in scrotum; blood
supply: testicular artery surrounded by venous network (pampaniform plexus)
facilitates temperature regulation
- lobules contain seminiferous tubules (site of spermatogenesis) (fig. 80 – 2 &
ppt. 2)
- endocrine interstitial cells of Leydig (source of androgens) (figs. 80 - 7,
80 - 8 & ppts. 3 & 4)
- epididymis: secretes seminal fluid (about 10% of semen) connects testis
with vas deferens (sperm duct); approx. 6 meters of coiled tubules in epididymis
- vas passes into body within spermatic cord & loops medially over ureter to
descend posterior wall of urinary bladder; surgical interruption = 'vasectomy'
• accessories: seminal vesicles empty into proximal parts of vasa deferentia;
secrete seminal fluid (approximately 60% of volume of semen)
- prostate gland: receives urethra from urinary bladder and is site of
junction of vasa deferentia with urethra (combined reproductive and urinary
passageway from this point to exterior); secretes prostatic fluid (about 30% of semen)
- bulbourethral glands: join urethra near bulb of penis; secrete mucus
- urethra extends from urinary bladder through prostate (prostatic part),
pierces urogenital diaphragm (membranous part), and passes out penis to exterior
(spongy part); combined reproductive and urinary passageway
• penis (fig. 80 - 6 & ppt. 5): copulatory organ composed of three masses of
erectile tissue:
- corpus spongiosum: features proximal swelling (bulb) and distal swelling
(glans); conveys urethra to exterior; glans may be covered by prepuce (foreskin)
- corpora cavernosa: dorsal masses; diverge proximally (crura of penis)
2.
Physiology of Male Reproduction:
• spermatogenesis (fig. 80 - 2 & ppt. 6):
- spermatogonia (diploid sperm mother cells) at periphery of seminiferous
tubule ---> primary spermatocytes (diploid cells that enter meiosis I) ---> secondary
spermatocytes (haploid cells that enter meiosis II) (fig. 80 - 3 & ppt. 7) ---> spermatids
(haploid cells that mature into spermatozoa (fig. 80 - 4 & ppt. 8); maturation =
spermiogenesis)
- latter processes occur in intimate association with nutritive sustentacular
(Sertoli) cells
PMD 604, lec 10
- p. 2 -
- spermatozoa: headpiece includes condensed male pronucleus (haploid set of
chromosomes, including either X or Y)
- acrosome (specialized lysosome) aids penetration of egg membranes
during fertilization
- tail is composed of a flagellum (with typical core of microtubules); proximal
part also contains mitochondria that provide energy (ATP) to support tail motility
• hormonal relationships (fig. 80 - 10 & ppt. 9):
- gonadotropin releasing hormones: (from hypothalamus) regulate
pituitary gonadotropins:
- follicle stimulating hormone (FSH): stimulates spermiogenesis in testis;
collaborates with testosterone to promote spermatogenesis
- luteinizing hormone (LH): supports testosterone secretion by interstitial cells
- human chorionic gonadotropin (hCG): (from placenta) stimulates
testosterone secretion in genital ridge & embryonic testes in fetus; Y chromosome
contains sex-determining region (SRY) that codes for SRY protein
- SRY protein promotes male developmental pattern
- testosterone: promotes development of primary reproductive structures (acts
in fetus, neonate & resumes in adolescents & adults) (fig. 80 - 9 & ppt. 10)
- promotes growth & proliferation of spermatogonia, development of
secondary sex characteristics (e.g., distribution of body hair, including baldness
based on genetics, muscular hypertrophy, enlargement of larynx)
- inhibin: (from Sertoli cells) imposes negative feedback inhibition of
hypothalamic-hypophysial-gonadal axis (especially FSH) to control rate of
spermatogenesis
• erection and orgasm: penis (normally flaccid, inferiorly directed) becomes rigid
and erect during sexual excitation (evoked by sensory stimuli from external genitalia
as well as psychic stimuli)
- parasympathetic nerve activity causes hyperemia of erectile tissues
producing an erection (renders penis suitable for intromission and deposit of semen
in female reproductive tract); PNS nerve endings may release or trigger secretion of NO
(vasodilator)
- sympathetic nerve signals cause emission & ejaculation (sexual climax)
3.
Anatomy of Female Reproductive Tract (figs. 81 - 1, 81 - 2 & ppts. 11 & 12):
• ovaries (fig. 81 - 4 & ppt. 13): primary sex organs in pelvis; produce ova;
secrete sex hormones
- primordial follicles (primary oocyte + granulosa cells) are formed at birth
from germinal epithelium (oogonia)
- granulosa cells nourish ovum & produce estrogens & progesterone
- primary follicles: growth of ovum & development of additional layers of
follicle cells (granulosa cells & thecal cells)
- vesicular follicles: follicles secrete fluid into developing cavity (antrum);
also secrete estrogens, which increase sensitivity to gonadotropins & accelerate growth
of follicles
PMD 604, lec 10
- p. 3 -
- mature follicle: only one (of perhaps a dozen follicles that commenced the
cycle) will 'ripen' to be ready for ovulation; bulges at surface of ovary (stigma) &
erosion of surface follicle cells permits bursting & release of ovum with associated
granulosa cells (corona radiata); triggered by LH surge (figs. 81 - 3, 81 - 5 & ppts. 14 &
15)
- corpus luteum: follicle cells remaining in ovary following ovulation,
undergo luteinization, a process that includes lipid accumulation & synthesis of larger
amounts of progesterone
PMD 604, lec 10
- p. 4 -
• uterus (fig. 81 - 1, 81 - 2 & ppts. 11 & 12):
- composed of body, fundus & cervix; wall is comprised of perimetrium,
myometrium & endometrium
- endometrium passes through cycles of buildup (proliferative phase),
secretion (secretory phase) & deterioration with sloughing of necrotic material
(menstrual phase) (fig. 81 - 8 & ppt. 16)
- uterine tubes: terminate near ovaries with fimbriae at ends & ciliated lining
• vagina (birth canal): inferior to uterus, lined with stratified squamous
mucosa
• vulva: labia majora and labia minora enclose vestibule containing clitoris
(homologue of penis), opening of urethra and vaginal orifice (fig. 81 - 1 & ppt. 11)
4.
Mammary Glands:
• modified sweat glands serving to produce milk to nourish newborn
- glandular units (alveoli) empty into lactiferous ducts that communicate
with openings in the external nipple (surrounded by areola); development stimulated by
estrogens, but final maturation & function depends on progesterone & prolactin
5.
Physiology of Female Reproduction:
• hormonal relationships (figs. 81 - 10 & ppt. 17):
- hypothalamus hormones: gonadotropin releasing hormones that regulate
pituitary gonadotropins
- anterior pituitary hormones: follicle stimulating hormone (FSH): for follicle
growth in ovary
- luteinizing hormone (LH): for follicle maturation, estrogen secretion &
progesterone secretion (fig. 81 - 7 & ppt. 18)
- LH surge (near mid cycle) causes ovulation; LH stimulates follicular
residue to form corpus luteum, which secretes progesterone and some estrogens; LH
maintains corpus luteum
- ovarian hormones (figs. 81 - 6, 81 - 7 & ppts. 18 & 19): prior to ovulation
(follicular phase), ovary secretes mainly estrogen with some progesterone just before
ovulation; after ovulation (luteal phase), ovary secretes predominantly progesterone (fig.
81 - 3 & ppt. 14)
- estrogens: proliferation of mammary glands and glands of
endometrium; enlargement of pelvic dimensions, development of secondary sex
characteristics (female distribution of body fat, rapid but shortened growth in early
puberty, development of pubic and axillary hair)
- progesterone: promotes secretion by mammary gland & by
endometrium
• ovarian cycle (ppt. 21):
- follicular phase (preovulatory phase): (approx. first 14 days) follicles enlarge,
become vesicular with primary oocyte completing first meiosis; mature follicle (ready
for ovulation); mostly directed by FSH from anterior pituitary with help of LH
PMD 604, lec 10
- p. 5 -
- luteal phase (post ovulatory phase): LH surge triggers ovulation and
development of corpus luteum; progesterone level rises and produces a
strengthening of estrogen's negative feedback on anterior pituitary inhibiting further
output of gonadotropins; inhibin, also produced by granulosa cells exerts feedback
inhibition (especially of FSH)
PMD 604, lec 10
- p. 6 -
• uterine cycle (fig. 81 - 8 & ppts. 16 & 21):
- proliferative phase: estrogens promote thickening of endometrium (rich
blood supply, extensive glandular development)
- secretory phase: progesterone from corpus luteum promotes glandular
secretion, preparation of endometrium for implantation
- menstrual phase: in absence of implantation, negative feedback on anterior
pituitary causes deterioration of ovarian corpus luteum and resulting decline in
progesterone leads to sloughing off of endometrium constituting the menstrual
discharge (4 - 5 days)
• regulation of non-pregnant reproductive cycle: (ppts. 20 & 21)
- following menses, pituitary FSH and LH rise, initiating next follicular
phase of ovary
- estrogens from maturing follicles promote proliferative phase of uterine
endometrium
• rising estrogen levels cause positive feedback upon anterior pituitary
causing gonadotropin surges (especially LH); ovulation ensues
• corpus luteum formation in ovary marks beginning of luteal phase with
progesterone dominating hormonal picture
• progesterone promotes secretory phase of uterine endometrium and
potentiates estrogen's negative feedback inhibition of AP gonadotropins
• corpus luteum regresses (lack of LH support); endometrium deteriorates
with lack of progesterone support; menses begins